Belt retractors for motor vehicles essentially comprise a belt reel for receiving the belt itself and a housing frame in which this belt reel is supported. The housing frame also serves to anchor the retractor to the vehicle body or to structural parts of a vehicle seat. This housing frame is typically embodied as a bent sheet-metal part and also serves to receive and anchor the components of the locking device, the drive spring, and other—application-specific—components.
From European Patent Disclosure EP 1 637 413 B1, which generically defines the prior art, it is known to make the housing frame for a seat belt retractor as a plastic component. To that end, this seat belt retractor is said to be embodied as an injection-molded part, and a fiber-reinforced thermoplastic material is contemplated as the plastic material. This housing frame is embodied as a closed rectangular frame, which on one side has an open receiving chamber for the drive spring and on the opposite side has an open receiving chamber for the components of the locking device. The belt reel is inserted into this housing from an open face end, and for this purpose the structural length of the belt reel in the axial direction is less than the spacing of the two side walls. The support of the belt reel is accomplished by a shaft inserted through it, and the shaft can additionally have the function of a torsion bar.